CB1激动剂延长雌激素替代治疗改善学习记忆时间窗的分子机制

Cognitive impairment can be alleviated in postmenopausal woman treated with estrogen. However, clinical studies have shown that estrogen replacement therapy (ERT) is ineffective in long-term menopause and has time window phenomenon. Long-term deficiency of estrogen leads to the loss of estrogen receptor ERα in female brain, which may be related to the ineffective treatment of estrogen and the aggravation of cognitive impairment in patients. Our previous study found that the learning and memory were declined after long-term ovariectomy, and continuous estradiol treatment could improve memory acquisition but block extinction of memory in mice. Treatment with estradiol caused the impairment of LTD induction in the hippocampus of mice after long-term ovariectomy. Combined application of cannabinoid CB1 receptor agonist ACEA with estradiol rescued the effect of estradiol on learning and memory and recovered LTD induction in the hippocampus. These results suggest that CB1 may be involved in the decline of learning and memory induced by long-term estrogen deficiency. We hypothesize that CB1 could be a potential drug target to reverse the reduced sensitivity of estrogen treatment and prolong the time window of ERT in improving learning and memory. In present study, multiple methods combining electrophysiology, molecular biology, and behavioral tests will be employed and Cnr1 gene knockout mice will be established to study the interaction of ERα and CB1, and reveal the mechanisms underlying CB1 regulation of ERT time window in long-term menopause. This project will provide a new therapeutic strategy and theoretical basis for clinical application of ERT.

女性更年期采用雌激素替代治疗能够最大程度降低认知功能减退，然而临床研究表明长期绝经后雌激素替代治疗效果不佳，存在时间窗效应。长期雌激素缺失可导致女性大脑雌激素受体ERα丢失，可能与雌激素治疗无效甚至加重患者的认知障碍相关。我们前期研究发现，长期去势小鼠学习记忆受损，雌二醇连续治疗改善了小鼠记忆获取，但影响记忆消退并伴有海马LTD诱导障碍；联合应用大麻素受体CB1激动剂ACEA可以恢复雌二醇改善学习记忆的作用以及海马LTD诱导，结果提示CB1可能参与了雌激素长期缺失引起的学习记忆减退。本项目提出假说：大麻素受体CB1可作为潜在的药物靶点逆转雌激素治疗敏感性降低，延长雌激素改善学习记忆的时间窗。本研究拟采用电生理学、分子生物学和行为学等方法，建立特异性基因敲除小鼠，深入研究雌激素受体ERα与CB1的相互作用，揭示CB1调控雌激素治疗时间窗的潜在机制，为临床雌激素替代治疗提供新的策略和理论依据。

女性更年期综合征是由于女性卵巢功能逐渐减退直至完全丧失引起的一系列临床症状，如阵热潮红、冠心病、糖尿病、骨质疏松、神经及精神障碍（情绪失常、易激动、记忆力减退、焦虑和抑郁）等。大约有1/3以上中老年女性会发生更年期综合征，严重影响了生活质量。用雌激素（或雌激素+黄体酮）治疗女性更年期综合征在全世界仍然非常普遍。然而，越来越多的研究表明：妇女绝经早期采用雌激素替代治疗（Estrogen Replacement Therapy, ERT）能够显著减少冠心病发病率及死亡率，预防骨质疏松，并能最大程度减少认知和情绪改变，有益于认知功能和海马可塑性。然而，雌激素的治疗作用随着绝经时间延长而减弱甚至还能增加痴呆的发生，显示绝经期雌激素替代治疗具有时间窗（Time window）效应。如何延长雌激素治疗时间窗并恢复雌激素治疗敏感性，是临床关注热点问题，深入研究其机制具有重要的临床价值。.我们的研究表明，长期去势小鼠学习记忆受损，CB1表达减少，雌二醇连续治疗改善了小鼠记忆获取，但影响记忆消退并伴有海马LTD诱导障碍；联合应用大麻素受体CB1激动剂ACEA可以恢复雌二醇改善学习记忆的作用以及海马LTD诱导，结果提示CB1参与了雌激素长期缺失引起的学习记忆减退。进一步研究发现，CB1在转录水平没有变化，CB1水平降低可能与转录后的机制相关。高通量RNA测序显示miR-221-5p水平减弱，其靶向E3泛素蛋白连接酶Neurl1a和Neurl1b。E3泛素蛋白连接酶活性升高，导致CB1泛素过度，在长期雌激素缺乏小鼠中以逆行的方式破坏了eCB系统。因此，miR-221-5p的过表达或协同激活CB1可能被证明是延长绝经妇女的雌激素治疗时间窗的潜在策略。在本研究中，我们确认了CB1在接受雌激素治疗的长期去势小鼠恐惧消除中的重要性，为临床雌激素替代治疗提供新的理论依据。